As a conventional technique relevant to this invention, Japanese Unexamined Patent Application Publication (JP-A) No. 2003-149793 is cited. According to the technique described in this publication, it is described that a blank maker classifies blanks by defect ranks according to inspection results and supplies the blanks to a mask maker while attaching defect information.
On the other hand, Japanese Unexamined Patent Application Publication (JP-A) No. 2003-248299 discloses a technique for accurately locating a defect position on a photomask substrate.
In these conventional techniques, although the defect information provided along with the mask blank shows the relative position relationship between defects existing on the mask blank surface, there is provided no reference for correspondence between the mask blank and the position information of the defect information. Therefore, even if there is the defect information, it is not possible to accurately locate where the defects exist on the actual mask blank and, hence, pattern failure occurs in the writing/development process. Further, there is no definite guarantee in terms of providing agreement between a direction of the mask blank placed in a receiving case and a direction of the defect information. Therefore, the actual mask blank and the defect information are deviated by 90 degrees, 180 degrees, or 270 degrees so that the pattern failure occurs in the writing/development process. This is because, in the manufacturing process, after taking out a substrate placed in a container such as a distribution case, a cassette, or a receiving case and applying predetermined treatment thereto, when placing it again in another container, there is no means for confirming that the direction of the placed substrate is the same in the former container and the latter container.
Conventionally, there has been no particular disadvantage with such defect information in fabrication of masks by a mask maker. This is because, in the case of a conventional exposure light source such as i-line (wavelength 365 nm) or KrF (wavelength 248 nm), the allowable defect levels, i.e. the allowable ranges of the size and number of defects, are not so narrow.
However, following higher integration of semiconductor devices, patterns are complicated and the line widths thereof are narrowed. In order to cope with it, the wavelengths of exposure light sources are shortened and ArF (wavelength 193 nm), F2 (157 nm), and so on are examined as light sources, and as a result, it is expected that the allowable defect levels for masks will be stricter than before.
Further, because of the complication and miniaturization of patterns, the time and cost required for manufacturing a mask by writing a pattern with a writing apparatus have been rapidly increasing. Therefore, the need has been increasing for suppressing pattern defects caused by mask blanks. As such pattern defects, there are, for example, defects called particles and pinholes.
On the other hand, as mask blanks adapted for the miniaturization of patterns, the demand for phase shift mask blanks has been increasing. In a halftone phase shift mask blank being one type of the phase shift mask blanks, there are formed a halftone film, a light shielding film, and further a resist film if necessary. The halftone film has a light shielding function and a phase shift function and thus has a role different from that of the light shielding film.
In order to achieve improvement in yield of the mask manufacturing process, simplification of the process, cost reduction, and so on, it is necessary to obtain defect information of each of the films forming the mask blank.
Patent Document 1:
    Japanese Unexamined Patent Application Publication (JP-A) No. 2003-149793Patent Document 2:    Japanese Unexamined Patent Application Publication (JP-A) No. 2003-248299